Quartz is really cool.

You know those white rocks you see every now and then when you're walking in our mountains? They are made of quartz, one of the coolest things ever! They can form beautiful crystals, they resonate when you put an electric charge across them, they create an electric charge when you squash them and it is possible to melt them in a very, very hot fire to weld other rocks together (although we can't work out how!).

Quartz is the most abundant and widely distributed mineral found on the Earth's surface. It is found everywhere and is plentiful in igneous, metamorphic, and sedimentary rocks. It is very durable, resisting mechanical and chemical weathering. As a result, it is very often found on mountain tops and is the primary constituent of beach, river, and desert sand.

These are some quartz crystals I found in the Alps. Quartz is one component of granite, along with mica and feldspar. When granite cools down incredibly slowly, the minerals have time to come together to form big crystals. The slower it cools, the bigger the crystals. Some quartz crystals are 50cm long and crystal hunters still work in the mountains of the Alps. Quartz is a chemical compound made up of silicon and oxygen (SiO2 - silicon dioxide or silicate) and the molecules are perfectly lined up in a crystal, in the same way that carbon atoms are lined up in diamonds.

So, why is the quartz we see in our hills white, and not crystaline? Well, imagine the crystaline quartz is a car windscreen. When you hit it, what happens? It fractures along lots of lines that criss-cross and make it look white. It's the same with our quartz. It has so many imperfections in it, so many fractures and layers, that the light going through it is refracted and reflected inside, making it look white.

Watches used to advertise the fact that they rely on quartz. Quartz resonates (vibrates) at a specific frequency when you pass an electric charge across it. It is possible to use this resonance at a known frequency to set the speed of a watch. The frequency does not change, even when the electric charge changes so it is a very reliable method to use for measuring time. 

Quartz is a pietzoelectric material. This means it creates an internal electric charge when you apply mechanical stress. Squash quartz and you can make an electric charge sufficient to cause it to spark. You have probably done this when you light a gas stove. Jetboil stoves have them; the little button you press squashes a pietzoelectric material to make the spark.

Sitting high above Glen Nevis, Dun Deardail is one of Scotland's 70 ancient vitrified forts. There are very many hill forts, but the vitrified forts are different in that they have been burned at a very high temperature for enough time for the rocks to melt and stick together.

The process of vitrification occurs when a timber-framed drystone rampart is destroyed by fire. With temperatures reaching over 1000° C, the heat from the blaze begins to melt the rubble core of the rampart. As the burning rampart collapses, the rocks first fracture and then become liquid. Gas bubbles form inside the rocks as the extreme temperatures change their mineral composition. When the fire burns out and the rampart finally cools, the burnt and molten rocks form large blocks of conglomerated stone. These can still be seen within the rampart.

Vitrification is not a deliberate construction method as the original timber-framed drystone rampart would have been more stable; it is much more likely to have been the result of accidental fire or deliberate destruction. In recent excavations coordinated by Nevis Landscape Partnership, rocks of different types were found stuck together with quartz.

The Fort from Nevis Landscape Partnership on Vimeo.

So, next time you see some white rock, stop and look to see if it is quartz. Wonder at its amazing properties. Look to see if it is slightly transparent and crystaline. Imagine finding a crystal cave in which the walls, ceiling and floor are covered in quartz crystals, hundreds of millions of years old, that took millions of years to form. Be amazed by its electrical powers. Quartz is cool.